The present invention relates generally to hermetic compressors of the type having a hermetic housing, wherein a hermetic terminal is provided for carrying electrical current into the housing. More particularly, the present invention pertains to a terminal block assembly for making an electrical connection to the hermetic terminal on the interior of the housing.
Generally, a hermetic electrical terminal is installed in an opening in the housing of a hermetic compressor so that current may be carried to the compressor motor from an external power source. The terminal typically comprises a cup-shaped metallic body member and a plurality of conductor pins which extend through spaced apertures in the body member and are hermetically secured thereto by means of an insulating material. The hermetic terminal is inserted into the opening in the compressor housing with the open end of the body member facing the interior of the housing. The side walls of the body member are then hermetically attached to the housing, as by welding.
When a hermetic compressor having the aforementioned hermetic terminal is operably incorporated within a refrigeration system, metallic particles that may be suspended in the refrigerant fluid are attracted to the terminal, i.e., the surface of the insulating material, by a phenomenon known as electrophoresis. In some instances, an accumulation of the metallic particles on the surface of the insulating material establishes a conductive path, e.g., a short circuit or a ground fault, that may ultimately result in failure of the hermetic terminal.
Other contaminants within the refrigeration system, such as moisture and acidic components resulting from partial decomposition of the refrigerant fluid, are capable of attacking the surface of the insulating material of the hermetic terminal, thereby causing or contributing to electrical breakdown and failure of the terminal. In the event of a compressor motor failure accompanied by high temperatures within the compressor housing, a carbon mixture deposits on the inside of the hermetic terminal to form a conductive path that short-circuits or establishes a ground fault for the conductor pins of the hermetic terminal.
Prior art attempts have been made to shield the conductor pins of a compressor hermetic terminal from contaminants by providing a planar shield member to fit over the conductor pins and cover the open end of the terminal body member prior to making electrical connection with the conductor pins. A problem with some shields is that contaminants can still accumulate on the shield and establish undesirable conductive paths.
Some prior art connectors for making an electrical connection to the conductor pins of a hermetic terminal on the interior of the compressor housing generally have not been effective in protecting the terminal from contaminants or minimizing the dangers associated with failure of the hermetic terminal. Specifically, some prior art connector plugs and terminal block assemblies may not adequately isolate the interior open end of the cup-shaped body member from the environment within the compressor housing.
The present invention is directed to overcoming the aforementioned problems associated with electrical hermetic terminals for hermetic compressors, wherein it is desired to protect the pin-retaining insulating material from contaminants that may lead to failure of the terminal, and to minimize the damage resulting from such terminal failure should it occur.